In a processing line for performing predetermined processing with respect to, e.g., components of an electronic device or a machine, an operator mounts an object such as a rack accommodating such components on a carriage and then carries and delivers to each processing area (or an adjacently arranged transfer device), and receives processed objects (components) from a processing area (or a transfer device) and mounts them on a carriage and then carries to the next processing area, and the same operations are repeated.
Here, to assuredly transfer each object, the carriage must be securely positioned with respect to the processing area (or the transfer device).
As a conventional technique for positioning a carriage with respect to a processing device (a transfer area), there is known a technique of providing a positioning pin at an underside of a front surface of the processing device, forming a positioning hole at an underside of a front side of the carriage, and positioning the carriage with respect to the processing device when an operator moves the carriage closer to the processing device to fit the positioning pin into the positioning hole (e.g., Patent Document 1).
In this carriage and the processing device, a table on which an object is mounted, a motor that moves the table up and down, a transfer mechanism that transfers the object, and features are provided with regard to the carriage, the carriage is positioned, and then the table is appropriately moved up and down so that the object can be grasped by the transfer mechanism to be transferred to the processing device.
However, when this positioning technique is adopted, since the carriage is positioned with respect to the processing device in a state that (each wheel of) the carriage is in contact with a floor surface, its positioning accuracy is dependent on flatness of the floor surface. Therefore, the carriage may not be highly accurately positioned if the floor surface is not flat.
Further, in this transfer technique, since the elevation motor and the transfer mechanism are provided to the carriage, a dedicated carriage is necessary, which results in an increase in cost. When a carriage must be prepared for each object, in particular, a plurality of different types of carriages are required, leading to a further increase in cost.
As another technique for positioning a carriage with respect to a processing device (a transfer area), there is known a technique of providing a groove on a lower surface of a carriage and a protrusion on an upper surface of a frame in order to position the carriage integrally including a magazine accommodating components with respect to a transfer device (a stocker and an operation unit) including the frame capable of moving up and down and a pair of lifters that move the frame up and down. The carriage is moved up so as to be spaced from a floor surface and positioned while inserting the protrusion on the frame into the groove of the carriage and the carriage in positioned when an operator moves the carriage immediately above the frame with the frame being lowered and then operates the pair of lifters to move the frame up (see, e.g., Patent Document 2).
However, according to this technique, since the frame cannot be visually recognized when the carriage is moved to the upper part of the frame, it is difficult to position the groove of the carriage with respect to the protrusion of the frame, and moving the frame in a displaced state causes the carriage to be lifted in an inclined state, whereby an object possibly may not be assuredly transferred.
Furthermore, although the carriage is usually assembled in each production line (a factory) by an operator, an assembly error may arise at the time of assembly, or an assembly error intrinsic to each country may arise when the carriage is used in a production line (a factory) in each country. When the carriage has an intrinsic assembly error in this manner, utilizing the above-described conventional positioning technique may possibly result in a malfunction (e.g., a positioning error where a part of a carriage is caught by a part of a processing device and hence positioning cannot be performed) when positioning the carriage in a processing area (or a transfer device) or a malfunction (e.g., a positioning error where a part of a carriage is caught by a part of a processing device and hence positioning cannot be canceled) when canceling positioning of the carriage.
Moreover, distortion (inclination) or backlash is produced when a carriage assembled within a previously allowable dimension error range is repeatedly utilized in a production line (a factory) or the like over a long period. Therefore, a positioning error at the time of positioning the carriage or a transfer error at the time of transferring an object mounted on the carriage may occur when the carriage is continuously used in such a state, whereby production efficiency possibly may be lowered.    Patent Document 1: Unexamined Japanese Patent Publication No. 11-255321    Patent Document 2: Unexamined Japanese Patent Publication No. 60-262776